Analogue to Digital Converter Upgrade

for P3 data demodulator PCB


This is a user fitted ADC upgrade for the G3RUH MKII 400 bps P3 PSK Data Demodulator.

Its input is the bit detector's integrate-and-dump signal at TP3 and its output is a 9600 baud TTL RS-232 stream at 400 bytes/s for connection to a MAX232 or similar line driver.


In this way, detected PSK bits are available to a user's computer not only as binary decisions (0/1), but also with an additional 7 bits of detection quality information. The 400 byte/s stream of symbols is now processed in the user's computer to:

* Decode the standard AMSAT P3 telemetry block format; in effect, user software implements the functionality of the 3rd page of the P3 PSK Data Demodulator schematic.

* Decode other formats, notably Forward Error Correction (FEC) transmissions from the AMSAT Oscar-40 and future 400 bps PSK Phase III satellites such as 2018 Nov 15: P4A / Es'hail-2

Authors of popular Oscar-40 telemetry display programs have upgraded their software to handle this ADC modification. It will decode both the Standard and FEC encoded telemetry formats via the ADC.

Parts Supplied

The components required are available as a kit which includes:


The ADC Upgrade Kit is included with the purchase of made-up and tested demodulator boards.

Additional ADC information

Reference FEC Decoder

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Last updated: 2020 Jul 05